Brake Drive

ABSTRACT

A braking drive for a control cable or shaft has a drive shaft with a radial journal. A contractible brake ring has opposing ends defining a gap, with the journal in the gap The ring has an exterior surface biased outwards and two interior detents. A stationary interior housing circumscribes the ring, with an interior surface in frictional contact with the ring. An exterior portion of the housing has bosses being disposed within the detents of the ring. Friction between the ring and the housing interior arrests rotation of the journal and drive shaft until a force on the exterior portion of the housing moves the bosses, transferring the force to the ring via the detents, whereby the ring is contracted, releasing the frictional brake between the housing and the ring, thereby allowing rotation of the drive shaft.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. applicationSer. No. 09/802,516 filed Mar. 9, 2001 that claims priority to PCTApplication Number PCT/EP99/06747 filed Sep. 13, 1999, that claimspriority to Austrian Application Number A1537/98 filed Sep. 11, 1998.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] None.

BACKGROUND OF THE INVENTION

[0003] The invention relates to brake drives (reverse brakes) which canbe employed in many engineering sectors, for example as adjusting andfixing devices in machines, medical instruments and equipment, sportsand household devices, control mechanisms, for chairs and other items offurniture, in vehicles, aeroplanes, car seats etc. These brake drivescan be actuated by both a hand wheel 6 and by a control lever (6 a inFIG. 5) or by electrical, pneumatic, hydraulic or any other switching orcontrol elements which are not shown.

[0004] The object of the invention is to create brake drives which canbe designed in a simple and cost-effective manner owing to theirconstruction and optimal brake pressure distribution, and can also bedesigned in plastics material, zinc injection moulding or aluminiuminjection moulding, i.e. from less rigid material (parts 1 to 6 a) andcan be adjusted and fixed by both a hand wheel (6) and by a controllever (6 a in FIG. 5) or by electric, pneumatic, hydraulic, magnetic orany other switching or control elements (not shown) from the primary ordrive side “by entraining the drive side, for example shaft (3″) in bothdirections, in other words against a blocking or braking force, with thesmallest amount of slippage between primary rotational movement(adjustment or actuation) and secondary reverse locking or movement, forexample at a drive or driven shaft (3). A forward or reverse movement,each rotational movement of the drive and driven shafts can be severelybraked or completely blocked and released again as quickly as desiredand at any time depending on the design and adjustment. Thedisadvantages or weaknesses of brake drives and overrunning-type brakesaccording to the current state of the art are avoided by the subject ofthe invention.

[0005] Up until now, brake drives had inter alia multi-threadedcylindrical helical springs as braking element, which springs graduallyexpand along a stationary drum cylinder from one spring winding to thenext owing to circular pressure (for example anticlockwise) on one ofthe two spring ends in a stationary drum cylinder until all windings aregradually jammed against the stationary drum and block further rotationin the same direction. Owing to a circular tensile force at the otherend of the same brake spring (understandably only with slippage withrespect to the preceding circular force of pressure at the other springend), the individual spring windings can gradually be spooled onto asmaller cylindrical external diameter of the spring and jamming orblocking against rotation of the spring and therefore of a potentialdrive shaft are gradually cancelled only with an undesirable slippagepath.

[0006] This dead rotational slippage between releasing, rotating andblocking in previous reverse brakes constitutes a big disadvantagecompared with the present “Brake Drive” invention. A furtherdisadvantage of these multiple springs is that only a very thin,circular, external line of the individual helical spring windings, inother words a very small face, is supported on the housing innercylinder, as a result of which, a high rigidity material such as steelor the like must be used as a spring and also for the brake drum (as alarge specific force has to be exerted by the mini-friction face of thespring onto the cylindrical friction face).

[0007] A further significant disadvantage is that “a large amount” ofunused space and unused cylindrical friction face of the housing, inother words unused brake drum face between the thin actual springfriction faces, is wasted between the very thin, helical friction facesof each individual helical spring winding supported tangentially on thebrake cylinder.

[0008] The hitherto conventional overrunning roller-type or overrunningball-type brakes require a similar waste of space and unnecessarilyrequire an extremely high level of material rigidity (and are thereforegenerally made of steel and with expensive, and the highest levels ofprecision), which brake types all operate only with point application interms of material even when the largest braking or blocking force isdesired.

[0009] Shoe brakes have the disadvantage inter alia that theircylindrical friction faces are constantly rigid in diameter and in thecurvature with the housing internal cylinder curvature do not achieve areally saturated specific force of pressure applied uniformly to theentire brake periphery or cannot guarantee this over a prolonged periodof time. For this reason nearly all shoe brakes must comprise anadditional compressible material (the brake linings) between the shoebrake face and the drum inner cylinder brake face which also has to bereplaced with prolonged use.

[0010] Advantageous embodiments of the present “Brake Drive” inventionare provided in the patent claims and sub-claims and the drawings and,in brief, provide the following advantages:

[0011] 1. Both “active” brake cylinder faces (5) are many times largerbecause they rest on one another “with their entire faces” withoutunused intermediate spaces and therefore can be used 100%.

[0012] 2. As a result, the specific surface pressure (per mm²) is sosmall that even plastics material, aluminium, zinc or other injectionmoulded materials or less rigid materials and more favourable productionmethods can be used for the active elements.

[0013] 3. The expanding ring (2) has no no-load operation (slippage)between blocking and releasing because (like a helical spring) it doesnot have to wind or unwind over a plurality of spring windings when itreceives a circular push at a brake cylinder end of the expanding ringto radially enlarge the diameter or the brake force and inversely,receives circular tensile force at the other pitch circle end of thebrake cylinder once to reduce the expanding ring diameter and thereforeto lift the brake in order to be able to adjust the brake drive.

[0014] 4. The entire one-piece expanding ring (see FIG. 1) can also bedesigned as a double ring as in FIG. 3 and with and without additionalexpansion springs (9), (9′), (9″), (see FIG. 2) and can also be ofmulti-layered laminated design and despite this retains all theadvantages of the new brake drive.

[0015] 5. The expanding ring (2) which, with its larger externalcylinder diameter, was squeezed upon installation into the smallerinternal cylinder of the brake drum (1), has (in contrast to rigid shoebrakes) the active snap force (expansion force) at all points of itsfriction cylinder periphery, in addition to the normal applicationforce, to convert itself from a smaller radius into a larger radius bymeans of its inherent tendency and its stored force. Owing to thepreviously mentioned advantages alone, the brake drives according to thepresent invention rarely have any undesired slippage between control andblocking or braking any more, and this is in both primary and secondaryterms, in other words at the input and at the output side.

[0016] 6. Further advantages are given by an additional increase in thebrake force of the brake drive inter alia by, for example:

[0017] a) keyway-shaped inner and outer faces between expanding ring andhousing (transverse to the cylinder face, see FIG. 4 on the brake faces(5)) as a result of which an additional snap and braking effect orblockage is produced by the tapered rings in the opposing keyways at theentire periphery, as is the case with a V-belt.

[0018] b) Owing to symmetrical or asymmetrical micro or normal wavinessof one or both friction faces, in longitudinal direction or direction ofrotation of the circular brake faces (see FIG. 3, circular pictures aand b), a complete standstill against a rotation is achieved betweendrum (1) and expanding ring (2) with the slightest expansion, andrunning is again achieved with slight compression of the expanding ring.

[0019] c) Owing to such a symmetrical or asymmetrical micro- ormacro-waviness of one or both friction surfaces, or micro- ormacro-waviness extending in another way, an ideal state can be achievedfor many purposes, for example, in such a way that the brake driveitself (in other words, without but also with “counter-torque”) has alarger braking moment, for example in the anticlockwise direction (orclockwise direction) than in the other direction of rotation. As aresult, the torque for lifling a crane load, for example, can bedesigned so as to be smaller than that for rewinding the cable pull orother drive. The reverse movement is actually more sluggish than thelifting or tensioning process of, for example, a cable pull or otherdrive. This can also be achieved, for example, by an asymmetric sinecurve or the like which is gentler in direction of rotation, in otherwords flatter, and is steeper in the reverse direction and therefore hasmore braking power.

[0020] d) When the direction of rotation in which the brake drive shouldbrake or block is known, a starting aid can be provided at that end ofthe expanding ring friction face which is remote from the pressure pointof the driving journal (4) on the circular end face of the ring (2) andwhich is not pushed by the part (4) itself, for the start of brakingafter a lifting process, in other words a braking aid for the transitionfrom the lifted expanding ring position to the expanded, braked orblocked position (similar to a trimmer in ships, aeroplanes, etc.), bystart braking aids (see FIG. 3, parts 12 and 12 a). The parts (12) areribs which project slightly beyond the brake cylinder of the expandingring (2) which, after lifting in the event of a further braking orblocking wish, start to brake as first parts of the expanding ring (2)owing to their early contacting of the brake drum inner cylinder (5)(and also owing to their additional tilting). As a result, the remainingarc of the circle and brake face are brought more quickly and violentlyinto close contact and the entire ring is expanded or blocked as in achain reaction. The start braking aids 12 a operate in a similar manner.They comprise one or more additionally inserted or vulcanised-on, glued,dipped coatings with materials which project slightly and have a highercoefficient of friction.

[0021] 7. An expansion element (see FIG. 6b) which has been producedfrom slightly resilient material and has also been squeezed, withexcessive diameter into the brake drum (1) and can only receivecounter-torques in “one” direction of rotation, can be rotated in bothdirections by a pivoted lever (6 a) (in other words, also against theblock) when owing to actuation of the lever or a pulled-on hand wheeletc., a shrink ring (13) can be reduced in diameter until the resilientexpansion element (2 b) with its segment indentations (14) is reduced indiameter by the shrink ring (13), which is cast or located in a groove,until it is loosened or lifted such that the pivoted lever (6 a)together with the expansion element (2 b) can rotate in the stationarybrake drum (1) which in turn then drives the driven shaft (3).

[0022] 8. To increase the expansion force of the expanding rings (2),expansion force intensifiers can be used (parts (10) in FIGS. 5, 5a and5 b) which intensify the braking or blocking force of the expanding ringowing to the counter-torque of the driven shaft (3). Owing to, forexample, contracting elements, such as the two contracting journals (6′)and (6″), which, for example, are securely connected to a contractingpivoted lever 6 a or are integral therewith, both the expanding ring (2)and the expansion force intensification lever (10′) or expansion forceintensification eccentric (10′) and the shaft (3) can be reversed, acontracting clearance (11) (play between brake internal and externalcylinder) can be created and the rotational position of the shaft (3)can also be adjusted and fixed again in both directions of rotation bymeans of its driving journals (4) with the same pivoted lever (6 a) orinstead of that, a pulled-on pivoted hand wheel (with the samecontracting journals (6′) and (6″)).

[0023] 9. The secondary reverse torque presses in a circular mannerexclusively on the inner end face of the expanding ring (2) via theshaft (3) and its driving journals (4) in such a way that it can onlyexert a torque on the expanding ring on the end face of the expandingring ends in a radially-pushing manner. Owing to the actuating elementor elements, this power arm lever can be used to adjust a brake driveand to restrain a circular force, in other words for braking or blockinga torque or rotating a shaft. The brake drive is installed as anembodiment in FIG. 1 to FIG. 4 in the free interior of a conventionallyhollow hand wheel (part 6) which can also be mounted, for example, foractuating or adjusting a car or office seat or any machine or anydevice, or with which a torque force automatically braked or blockedagainst reverse movement or rewinding is to be controlled. Such a handwheel (part 6) or such an adjusting lever (part 6 a in FIG. 5) or evenjust the brake drive alone (with or without other actuation elements)can be adjusted in both directions of rotation with driving of the shaft(part 3) without additional lifting of a brake or overrunning or othertype of brake or blocking device. When the hand wheel or the lever oractuating element for the brake drive is released, the brake drivebrakes or blocks automatically, in other words (depending on theadjustment and/or design, pre-tensioning, material use etc.) the brakedrive cannot reverse the adjusted rotational movement in a secondaryretroactive manner or can only do this in a severely braked fashion,from the driven shaft (3), after an adjusting force has been releasedafter a primary adjustment (by the hand wheel, the lever etc.).

[0024] The brake drive can, however, also be located inside any designat any point of a drive shaft or driven shaft (supported againstexternal torque by the environment or a cable pull, a spoke or otheranchorage) in such a way that the primary adjusting rotary force acts(primarily, in other words in an adjusting fashion), for example, bymeans of a second hollow shaft (not shown) (pulled over a projection ofthe first shaft 3) acting on the same axis or an adjusting shaftextending in an articulated manner at an angle to the main axis butequally for example, by means of a cable reel and Bowden wires, toothedwheel or other drive mechanisms inside a device, equipment, furniture,vehicle etc., wherein the driving or driven outgoing shaft (3) can beadjusted with the primary adjustment. Inversely, in other wordssecondarily, this shaft (3) cannot, however, (or, depending onadjustment, with greater or less ease) rotate this brake drive.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0025]FIG. 1 is a cutaway front view of the brake drive.

[0026]FIG. 1A is a cutaway side view of the brake drive.

[0027]FIG. 2 is a cutaway front view of another embodiment of the brakedrive.

[0028]FIG. 2A is a cutaway side view of another embodiment of the brakedrive.

[0029]FIG. 3 is a cutaway front view of yet another embodiment of thebrake drive.

[0030]FIG. 4 is a cutaway side view of yet another embodiment of thebrake drive.

[0031]FIG. 5 is a cutaway front view of another embodiment of the brakedrive.

[0032]FIG. 5A is a cutaway front view of another embodiment of the brakedrive.

[0033]FIG. 5B is a cutaway close-up front view of the journal and leverinteraction of the brake drive.

[0034]FIG. 5C is a cutaway close-up front view of the journal and leverinteraction of the brake drive.

[0035]FIG. 6 is a cutaway front view of another embodiment of the brakedrive.

[0036]FIG. 6A is cutaway side view of another embodiment of the brakedrive.

DESCRIPTION OF DRAWINGS

[0037]FIG. 1 shows in section A-A through FIG. 1a, a housing (1) withcylindrical inner face which serves as friction (or braking) face (5)and receives the open single expanding ring (2) which has itscylindrical friction surface (5) on the outer side. The predeterminedexternal diameter of the expanding ring (2) has a larger externaldiameter in the uninstalled state than the cylindrical inner frictionface (5) of the housing (1). After installation of the expanding ring(2) by compressing (pretensioning) and insertion into the housing (1),the friction faces (5) of the two components (1) and (2) press firmlyagainst one another, as a result of which the braking effect againstrotation of the expanding ring (2) is actually achieved in thestationary housing (1). A permanent torque which retroacts, for exampleby a mechanism which can be adjusted by means of the shaft (3), is,however, additionally braked until stopped in every position of theexpanding ring (2) by the driving journal (4). The driving journal (4)presses, namely with its support part (4′), in a circular andnon-positive fitting manner on the radial end face of the open expandingring (2) and therefore further intensifies its predetermined, inherentbraking torque or the braking effect between expanding ring (2) andhousing (1). This braking force or blocking is, however, weakened orcancelled by rotating the hand wheel (6) (with its contracting journals(6′), (6″) which are formed as one piece with the hand wheel or aremounted). These journals exert a circular tensile force on the otheropen end of the expanding ring (2) which reduces or cancels the snap andbraking force of the expanding ring (2). The hand wheel (6) can thencancel the blockage or braking effect in the reverse sequence via theexpanding ring (2), the application part (4′), the driving journal (4)and the shaft (3) arid allows the entire mechanism, i.e. the brakedrive, rotation and adjustment in both directions of rotation (alsoagainst a blockage)

[0038]FIG. 1a shows section B-B through the centre of FIG. 1. Thecircular pull hand wheel is pulled over the housing (1) and securedagainst removal by moulded-on catching lugs (7).

[0039]FIG. 2 and FIG. 2a show a brake drive as it is described in FIG. 1and FIG. 1a, however, the inherent expansion force of the expanding ring(2) is intensified by additional expansion elements, such as the springs(9), (9′), (9″) shown for example, which simultaneously increase thebraking effect. Three variations of expansion elements are shown by wayof example: 1.) The two helical springs (9) are located between the tworadial end faces of the aperture of the expanding ring (2). 2.) Adouble-threaded helical spring (9′), which is wound round the shaft (3)and the ends of which are extended, also presses with these ends againstthe two end faces of the expanding ring (2). 3.) A spring strip (9″)which is bent round with pretensioning and is inserted on the inside ofthe expanding ring (2). An embodiment which is not shown would be, forexample, an expanding material such as a rubber, foam material, aplastics material, an insulating air cushion, pneumatic springs etc.which can be inserted into the expanding ring to increase the expansionforce.

[0040] An example of a method of securing the entire brake drive throughthe base of the housing (1) with countersunk head screws (8) is alsoshown in FIG. 2a, wherein the view of the shaft (3) is interrupted.

[0041]FIG. 3 shows a further brake drive with a double expanding ring(2), the inner ring of which additionally applies an expansion force tothe friction face (5). Two variations of the design of the friction orbrake faces (5) are shown by way of example in the detail enlargements aand b. The waviness, by way of example, of the two friction faces (5)can have the same structure or a different structure both on the housing1 and on the expanding ring (2) and can be microphone or coarse and ofdifferent depth. The difference between the two examples is:

[0042] Variation a: the wave path is uniformly symmetrical. The sameresistance is encountered in both directions of rotation upon brakingand adjusting. Variation b: the wave path is steeper in ascent thandescent. Greater resistance is encountered in one direction and lessresistance is encountered in the other direction upon braking andadjusting. Therefore, a torque acting permanently or pulsatingly and inretroactive fashion on the brake drive in one direction can beintercepted, moderated, levelled better or, with regard to theadjustment force expenditure, be partially or completely reversed or canalso be stopped completely even with lower expansion force.

[0043] Owing to the design of the friction faces, the braking effect isintensified in addition to the friction and expansion force, because afurther force expenditure is required to overcome the gradient and wheneach wave is overcome the expanding ring (2) is pretensioned in eachcase by double the wave height. The fact that owing to the respective“engagement” in each wave trough, the sliding friction is partially tocompletely converted into a stationary friction and therefore thecoefficient of friction is increased towards the start of a reversal,also intensifies the effect.

[0044]FIG. 3 also shows braking start aids (12) and (12 a) which areonly applied individually and only start expansion of the expanding ringin one direction of rotation after the venting procedure (like a trimmerin ships), when they act on the other expanding ring end face which hasnot been pushed (owing to slight projection above the brake cylinder orowing to special brake material).

[0045]FIG. 4 shows a keyway-shaped, meshing design of the two frictionfaces (5) on the housing (1) and on the expanding ring (2). On the onehand, this enlarges the friction faces as a whole and, on the otherhand, the braking effect owing to the keying of the respective groovewith the opposing wedge. The peripheral keyways can also be designed asscrew threads for screwing the expanding ring (2) (expansion element)into a nut-like housing (1).

[0046]FIG. 5 shows a brake drive with double expanding ring (2) and acontracting pivoted lever 6 a which comprises two contracting journals(6′), (6″) integrally or securely connected to the contracting pivotedlever. The shaft (3) has a driver (4) (integral or loose), the end ofwhich engages in the aperture of the expanding ring (2) and transmits aretroactive torque to an expansion lever (10) via the shaft.

[0047] This expands the expanding ring (2), in addition to its owninherent expansion force (or else in the absence or relaxation of thesame), over the two, for example, radial end faces of the expanding ring(2) inside the housing (1), whereby the braking effect can be increasedup to blockage. By pivoting the lever 6 a (in either direction ofrotation), the double expanding ring (2) is compressed to a smallerexternal diameter owing to the two contracting journals (6′) and (6″)fixed in their spacing to one another and to the pivoted lever (6 a)(for example, by integral design of all three elements) but co-pivotingwith the pivoted lever (6 a), and as a result, the expansion force andbraking force is cancelled such that the pivoted lever always pivotsabout that contracting journal (6′) or (6″) as its fulcrum, which islocated on the same pivoting direction of the lever.

[0048]FIG. 5a shows the pivoted lever pivoted about the central pointand fulcrum of the journal (6″). It has driven the opposing contractingjournal (6′) about the same central point (6″). As a result, the entireexpanding ring (2) is again compressed (or contracted) (see air gap 11)to a smaller diameter owing to this circular eccentric movement andwedge effect between the two journals (6′) and (6″) with largertranslation through the lever (6 a) “against inherent and foreignexpansion forces”. The expansion intensification lever (10) is alsoreversed by the two inherent end faces of the expanding ring (2) againcompressed (together with the driven shaft (3)-via its driver (4)). Theentire brake drive together with the shaft (3) can now be rotated oradjusted towards both sides against or with an available counter-torqueon the driven side. When the pivoted lever (6 a) is released, theexpanding ring (2) immediately expands again, intensified or notintensified, for example by an expansion intensification lever (10), andbrakes or blocks, depending on construction, design, intention, thematerials used etc., a reverse rotation by the driven shaft (3) or acounter-torque.

[0049] The pivoted lever (6 a) can also be designed, as in FIGS. 1 and1a, 2 and 2 a and 3 and 4, without a lever by means of a hand wheel (6)pushed over the entire brake drive when sufficient play is left betweenthe inner cylinder of the hand wheel (6) and the outer cylinder of thehousing (1) for slight pivoting about one of the two journals (6′) or(6″), instead of rotation about the central point.

[0050]FIGS. 5b and 5 c show, in each case, an expansion intensificationlever (10′) which can be rotated by its rotary journal part about itsfulcrum M when a counter-torque from the driven side presses from theshaft (3) by means of its driving journal (4). The expansionintensification lever in FIG. 5b has, as a result, for example, alreadyrotated the expansion intensifier (10′) and its eccentric pitch circleface additionally spreads apart the opposing faces of the same expandingring (2) at the point of contact of the tangent T and additionallypresses the end of the expanding ring (2) with its friction face ontothe housing cylinder face with this translation lever (10′). FIG. 5cshows that the expansion intensifier (10′) is again reversed about thefulcrum M in the reverse sequence when the expanding ring (2) (asdescribed in FIG. 5 a) contracts owing to a translation pivoted lever (6a), i.e. is again compressed to a smaller diameter.

[0051]FIG. 6 and FIG. 6a show an elastic expanding ring (2 b) made of aslightly resilient material, the outer cylinder of which, as with theprevious expanding rings (2) and (2 a), is greater in diameter prior toassembly than the internal diameter of the cylinder of the housing (1).After assembly, i.e. after this elastic expansion spring has beenpressed into the housing, an “inherent expansion or inherent brakingforce” is also already produced which is smaller in one direction ofrotation and substantially larger in the other direction of rotation. Bytilting the intermediate segment portions about their roots upon acounter-torque towards the indentations (14), owing to obliqueindentations (14), many individual “tilting expansion braking forces”are again created up to total blockage, in addition to their inherentexpansion and braking force. One or more circular shrink rings (13)arranged on or just below the brake cylinder periphery of the elasticexpanding ring (2 b) can reduce their own diameter and the elasticexpanding ring diameter by compressing and shortening their circularperiphery, for example with the aid of the pivoted lever (6 a) shown. Asa result, the braking or blocking force of the elastic expanding ring (2b) is also reduced and an adjustment of the entire brake drive togetherwith the driven shaft (3) anchored in the expanding ring (2 b) ispossible in both directions of rotation and also against the segmentportions and blocking force.

What is claimed is:
 1. A brake drive comprising: a drive shaft having ajournal extending radially from the longitudinal axis of said driveshaft; a contractible brake ring having opposing ends defining a gap,said gap being in rotationally driveable communication with said journalof said drive shaft, said contractible brake ring having an exteriorsurface and having at least one detent disposed within the circumferenceof said ring and said contractible brake ring having a structuraltension biasing said exterior surface outward; a housing circumscribingsaid contractible brake ring, said housing having an exterior portioncapable of receiving an external force and an interior portion having asurface in frictional contact with said exterior surface of said brakering, said exterior portion of said housing being moveable independentlyof said drive shaft and said interior portion of said housings saidexterior portion housing further having at least one boss fixedlyattached to said exterior portion of said housing, said boss beingdisposed within said at least one detent of said contractible brake ringin contracting cooperation therewith; whereby friction between saidexterior surface of said contractible brake ring and said surface ofsaid interior portion of said housing arrests rotation of said journalof said drive shaft until force on said exterior portion of said housingmoves said at least one boss of said housing, said boss transferring theforce to said at least one detent of said brake ring, whereby said ringis contracted, said contraction releasing frictional contact betweensaid surface of said interior portion of said housing and said exteriorsurface of said contractible brake ring, thereby allowing rotation ofsaid drive shaft, the force applied to said exterior portion of saidhousing being transferred through said at least one boss of saidhousing, said at least one detent of said contractible brake ring andagainst said journal of said drive shaft by one of said opposing ends ofsaid contractible brake ring, said movement of said boss being noncoaxial with said drive shaft.
 2. The brake drive of claim 1 furthercomprising an expander disposed between the ends of said brake ring andbiasing the ends apart.
 3. The brake drive of claim 1 wherein saidcontractible brake ring further comprises a plurality of concentrictensioning rings.
 4. The brake drive of claim 1 wherein the internalsurface of said housing and the external surface of said brake ring areirregular.
 5. The brake drive of claim 4 wherein topographic features ofthe internal surface of said housing and the external surface of saidbrake ring are disposed perpendicular to the direction of rotation ofsaid drive shaft whereby said surface topography resists rotation. 6.The brake drive of claim 1 wherein the exterior surface of said brakering has circular keyways and spline projections increasing brake force.7. The brake drive of claim 1 further comprising at least one boss onthe exterior surface of said brake ring.
 8. The brake drive of claim 1further comprising a layer of material fixedly attached to the exteriorsurface of said brake ring, said layer having an exterior surface infrictional communication with the interior surface of said housing, andsaid layer having a higher co-efficient of friction than said brakering.
 9. The brake drive of claim 1 wherein said housing furthercomprises a lever.
 10. The brake drive of claim 11 wherein said expanderis selected from the group consisting of: a lever, a cam, an eccenter, aspring, a pneumatic device, a hydraulic device, a magnetic device, andelectromagnetic device, a gear and a screw.